Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$133.76	7.261%	$143.4723	$143.47	$143.45	$143.50
Purchase #2	$71.37	10.216%	$78.6612	$78.66	$78.65	$78.70
Purchase #3	$84.85	8.363%	$91.946	$91.95	$91.95	$91.90
Purchase #4	$226.85	3.442%	$234.6582	$234.66	$234.65	$234.70
Purchase #5	$82.50	6.780%	$88.0935	$88.09	$88.10	$88.10
Purchase #6	$180.73	12.810%	$203.8815	$203.88	$203.90	$203.90
Purchase #7	$240.86	12.494%	$270.953	$270.95	$270.95	$271.00
7 purchase totals =	$1,020.92		$1,111.6657	$1,111.66	$1,111.65	$1,111.80